Split apart Functor into multiple files

After    | File Name             | Before
-------------------------------------------
0m06.82s | NaturalTransformation | 0m06.81s
0m02.31s | Functor/Composition   |   N/A
0m00.20s | Common                | 0m00.23s
0m00.15s | PreCategory           | 0m00.17s
0m00.11s | Functor/Core          |   N/A
0m00.08s | Utf8                  | 0m00.07s
0m00.06s | Functor               | 0m02.17s
0m00.06s | Notations             | 0m00.05s
0m00.05s | NotationsUtf8         | 0m00.04s
-------------------------------------------
0m09.84s | Total                 | 0m09.54s
Split up the files a bit more

After    | File Name                             | Before
-----------------------------------------------------------
0m03.85s | NaturalTransformation/Equality        |   N/A
0m02.10s | NaturalTransformation/Composition     |   N/A
0m02.01s | Functor/CompositionLaws               |   N/A
0m01.37s | NaturalTransformation/CompositionLaws |   N/A
0m00.25s | NaturalTransformation/Identity        |   N/A
0m00.21s | Functor/Composition                   | 0m02.10s
0m00.20s | Common                                | 0m00.16s
0m00.14s | PreCategory                           | 0m00.13s
0m00.12s | Functor/Core                          | 0m00.11s
0m00.11s | NaturalTransformation/Core            |   N/A
0m00.10s | Functor/Identity                      |   N/A
0m00.08s | NaturalTransformation                 | 0m06.25s
0m00.08s | Functor                               | 0m00.09s
0m00.06s | Utf8                                  | 0m00.08s
0m00.03s | Notations                             | 0m00.03s
0m00.02s | NotationsUtf8                         | 0m00.04s
-----------------------------------------------------------
0m10.73s | Total                                 | 0m08.99s
Add sum and product precategories

After    | File Name                             | Before
-----------------------------------------------------------
0m04.27s | NaturalTransformation/Equality        | 0m03.76s
0m02.47s | NaturalTransformation/Composition     | 0m02.26s
0m02.06s | Functor/CompositionLaws               | 0m02.04s
0m01.92s | SumPreCategory                        |   N/A
0m01.91s | ProductPreCategory                    |   N/A
0m01.36s | NaturalTransformation/CompositionLaws | 0m01.35s
0m00.26s | NaturalTransformation/Identity        | 0m00.30s
0m00.23s | Functor/Composition                   | 0m00.21s
0m00.19s | Common                                | 0m00.20s
0m00.16s | PreCategory                           | 0m00.14s
0m00.13s | NaturalTransformation/Core            | 0m00.11s
0m00.12s | Functor/Core                          | 0m00.12s
0m00.10s | NaturalTransformation                 | 0m00.07s
0m00.09s | Utf8                                  | 0m00.08s
0m00.08s | Functor                               | 0m00.08s
0m00.07s | Functor/Identity                      | 0m00.09s
0m00.05s | Notations                             | 0m00.04s
0m00.04s | NotationsUtf8                         | 0m00.04s
-----------------------------------------------------------
0m15.50s | Total                                 | 0m10.88s